1. Field of the Invention
The present invention relates to a solid-state laser apparatus.
2. Description of the Related Art
As a conventional solid-state laser apparatus, Japanese Unexamined Patent Publication No. 7 (1995)-302946 proposes a solid-state laser apparatus in which a solid-state laser rod doped with a rare earth element such as neodymium is pumped by a semiconductor laser device (laser diode). In the solid-state laser apparatus, an etalon is provided in a resonator as a wavelength selection element so as to realize a single longitudinal mode. Currently, solid-state laser apparatuses having such a construction are widely used.
In some solid-state laser apparatuses having the above construction, a nonlinear laser optical crystal is arranged in the resonator so as to convert laser light emitted by the solid-state laser rod, into a second harmonic wave, for wavelength conversion. Such solid-state laser apparatuses are also widely used.
However, when an excitation power is increased in order to obtain a high output power in the conventional solid-state laser apparatuses having an etalon in a resonator, oscillation of undesired wavelengths occurs at the same time as oscillation of a desired wavelength. For example, in a solid-state laser apparatus, when laser light having a wavelength of 1,064 nm is desired, oscillation of laser light having wavelengths of 1,075 nm and 1,085 nm occurs concurrently. In another solid-state laser apparatus, when laser light having a wavelength of 946 nm is desired, oscillation of laser light having a wavelength of 938 nm occurs concurrently.
When oscillation of undesired wavelengths occurs, a portion of a total energy is taken by the oscillation of undesired wavelengths, and therefore the output power at the desired wavelength is decreased. When the aforementioned wavelength conversion is performed, the power of the second harmonic wave is also decreased.